Effect of cryopreservation on sperm motility parameters and fertilizing ability of brown trout semen

• Brown trout semen can be effectively cryopreserved with glucose-methanol extender
• High post-thaw fertilization ability of semen at the sperm-to-egg ratio 300000:1
• Glucose-methanol extender can be universal for cryopreservation of salmonid fish

The aim of this study was to test the usefulness of 0.18 M glucose in 9% methanol as an extender, the ratio 1:5 (semen:extender) and an equilibration time of 15 min for the brown trout semen cryopreservation (n = 9). The final concentration was 0.15 M and 7.5% for glucose and methanol, respectively. Sperm motility parameters and fertilization rate at the eyed and hatching stages were assessed for post-thaw semen. The applied cryopreservation procedure resulted in remarkably high (73.8%) post-thaw sperm motility. The fertilization rate of cryopreserved brown trout semen was over 90% for sperm-to-egg ratios of both 300 000 and 600 000:1. To our knowledge, this study is the first to report the remarkably high post-thaw fertilization ability of brown trout semen at a sperm-to-egg ratio as low as 300 000:1. The described procedure for brown trout cryopreservation is highly reliable and efficient and therefore can be recommended for hatchery practice after scaling up this technique.